Clamping Force & Concrete Crosstie Bending Behavior Analysis FRA Tie and Fastener BAA - Industry Partners Meeting Incline Village, NV 7 October 2013 Sihang Wei, Daniel Kuchma
Slide 2 Outline Project Objectives Clamping Force Analysis Introduction UIUC clip instrumentation Clamping force calculation methodology Change of clamping force due to wheel load Clip strain diagram Conclusions Concrete Crosstie Bending Behavior Analysis Introduction UIUC concrete crosstie instrumentation Bending moment at rail seats and center Conclusions
Slide 3 Overall Project Deliverables Mechanistic Design Framework Literature Review Load Path Analysis International Standards Current Industry Practices AREMA Chapter 30 I TRACK Statistical Analysis from FEM Free Body Diagram Analysis Probabilistic Loading Finite Element Model Laboratory Experimentation Field Experimentation Parametric Analyses
Slide 4 Objectives of Clamping Force Analysis Experimentation Define the components of the clamping force vector Determine the range that the components of clamping force may vary under the following operating conditions: Clip installation Tangent and curvature Low speed and higher speed Round wheels and wheels with irregularities Determine how the change in clamping force effects the load path in the system
Slide 5 Background Clamping force as defined by manufacturer is the force applied by the clips vertically relative the rail seat Clamping force and clip behavior is examined in detail using finite element analysis Laboratory experimentation was used to validate the boundary conditions within the system model Clamping force as defined by the manufacturer is calculated via: R = D K where, R: Clamping force D: Vertical displacement at clip tip K: Stiffness of clip toe For Amsted RPS UAB2000 R = 2,375 lbs (expected) K = 8,223 lbs/in Finite-element model
Slide 6 Clamping Force Components Clamping force can be broken into two components Normal force (N) Tangential force (T) Normal force is The component of the clamping force normal to the clip toe Affected by the rail base rotation and rail pad assembly compression Tangential Force is The component of the clamping force tangential to the clip toe Affected by the rail base lateral translation and frictional interface between the clip and insulator
Slide 7 UIUC Clip Instrumentation and Force Calculation Methodology Clip strains were measured using strain gauges: Four (4) on each clip One (1) on both flat portions of clip, top and bottom Rail base vertical displacement, near the clip toe was measured using a potentiometer Change of force for each toe was calculated using the following methodology N D (1250 lbs / 0.289 in) G et eb Nd ( t / 2)cos EI T ( ) 2 EI d( t / 2)sin Where: D G is the gage side rail base vertical displacement e t is the strain measured at the top of the clip e b is the strain measured at the bottom of the clip d is the distance from clip contact to strain gauge
Force (lbs) Slide 8 Laboratory Experimentation Results: Change in Normal and Tangential Clamping Force Under Load An experiment was performed to investigate the change in clamping force components under varying load The gage-side normal and tangential clamping force components showed greater changes than the field-side components Gage-side clamping force components to be investigated in the field experimentation 200 150 100 50 0-50 -100 ΔNF/G: Change of normal force at field/gauge side ΔTF/G: Change of tangential force at field/gauge side 0 5 10 15 20 25 30 35 Load V (kips) 0-35 kips 2 kips ΔNF ΔNG ΔTF ΔTG
Slide 9 Instrumentation Location (Full Map) 1 2 3 4 A B C D E F G H I 5 6 7 8 9 10 11 12 P Q R S T U V W X Y Z 13 14 15 16 Rail Displacement Fixture Rail Longitudinal Displacement/Strains Pad Assembly Longitudinal Displacement Pad Assembly Lateral Displacement Insulator Longitudinal Displacement Insulator Vertical Displacement Steel Rods Vertical Web Strains Vertical and Lateral Circuits Shoulder Beam Insert (Lateral Force) Embedment Gages, Vertical Circuit, Clip Strains Crosstie Surface Strains MBTSS
Slide 10 Instrumented Clips 1 2 3 4 A B C D E F G H I 5 6 7 8 9 10 11 12 P Q R S T U V W X Y Z 13 14 15 16
Force (lbs) Slide 11 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 12 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 13 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 14 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 15 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 16 Change in Clamping Force 300 250 200 150 100 50 0-50 S E U W ΔN: change in normal force ΔT: change in tang. force 20 kips 40 kips
Force (lbs) Slide 17 Change of Clamping Force Under Dynamic Load Location: Tangent Equipment: Freight Speed: 2 mph 400 300 200 100 0-100 -200 EG_N EG_T SG_N SG_T UG_N UG_T WG_N WG_T 0 10 20 30 40 Axle # xg_n/t x: location (E, S, U, W) N/T: normal/tangential force
Force (lbs) Slide 18 Change of Clamping Force Under Dynamic Load Location: Curve Equipment: Freight Speed: 2 mph 400 300 200 100 0-100 -200 EG_N EG_T SG_N SG_T UG_N UG_T WG_N WG_T 0 20 40 60 Axle # xg_n/t x: location (E, S, U, W) N/T: normal/tangential force
Force (lbs) Slide 19 Change of Clamping Force Under Dynamic Load Location: Tangent Equipment: Freight Speed: 70 mph 400 due to flat spot on wheel 300 200 100 0-100 -200 EG_N EG_T SG_N SG_T UG_N UG_T WG_N WG_T 0 10 20 30 40 Axle # xg_n/t x: location (E, S, U, W) N/T: normal/tangential force
6722 Strain Diagram After Installation (Actual) The inner and outer calculated surface strain distributions 5240 shown in blue The inner and outer calculated surface strain values are listed in black The inner and outer recorded surface strain values are listed in red Recorded strain is very close to calculated strain Resulting clamping force components: N = 2740 lbs, T = -140 lbs Slide 20-6) Diagram Comparing for Contact with yielding Point strain = 5 (Inner of steel: Strain (1E-6) Surface) Diagram for Contact Point = 5 (Outer Su e f / E 183 ksi / 23000ksi 7957ms y 8694 7748 y 5486 2279 995.7 6722 8695 6641 8922 2874 3048 8694 7748 7647-7830 -8771 5486 2279 995.7 8695 6641 8922 2725 2874-3564 -3726-1446 -1099-1302 -1609-5575 -2376-1103 3048-2993 -3182 7647 5240 2725-7718 -5308-2788
3218 Slide 21 Yielding strain: Strain Diagram After Installation e f / E 183 ksi / 23000ksi 7957ms y y 7585 6551 4336 2058 3649 The strain distribution for inner and outer surface are shown below for case N = 2500 lbs, T = 0 lbs (assuming no tangential force) E-6) Diagram for Contact Point = 3 Strain (Inner Surface) (1E-6) Diagram for Contact Point = 3 (Outer S 6791 4710 1727 1336 3218-6851 -4775-1798 -1414-3304 7585 3649-7641 -3746 6551 4336 2058-6603 -4385-2104
8268 2753 Slide 22 The strain distribution for inner and outer surface are shown below for case N + N = 2500 lbs + 200 lbs, T + T = 0 lbs + 200 lbs E-6) Diagram for Contact Point = 3 (Inner Strain Surface) (1E-6) Diagram for Contact Point = 3 (Outer S 8768 Strain Diagram due to Typical Wheel Load Yielding strain: 7283 4732 e f / E 183 ksi / 23000ksi 7957ms y y 2242 3793 8268 6142 2927 464.1 2753-8286 -6161-2947 -487-2779 8768 3793-8785 -3822 7283 4732 2242-7299 -4746-2255
3011 Slide 23 9375 Strain Diagram Due to Impact Load Yielding strain: 7807 5078 e f / E 183 ksi / 23000ksi 7957ms y y 2407 4085 The strain distribution for inner and outer surface are shown below for case N + N = 2500 lbs + 400 lbs, T + T = 0 lbs + 200 lbs 1E-6) Diagram for Contact Point = 3 (Inner Strain Surface) (1E-6) Diagram for Contact Point = 3 (Outer S 8812 6519 3065 570.9 3011-8834 -6543-3091 -600.1-3043 9375 4085-9396 -4122 7807 5078 2407-7827 -5097-2424
Slide 24 Conclusions from Clamping Force Analysis Experimentation Clamping force can be represented by two orthogonal forces Normal and tangential The clamping force of a clip will not vary significantly when it is positioned two ties from the applied load The normal and tangential components of the clamping force do not change significantly under typical train operation Impact loads can impart significant strain into the clip The initial strain during installation may approach yield limit A more conservative design could be accomplished by closing up the gap between the two clip toes
Slide 25 Objectives of Crosstie Bending Behavior Analysis Experimentation Determine support conditions below crossties Determine the bending moments at the crosstie rail seats and the crosstie center when subject to: Static and dynamic loads Varying load magnitude (empty 315 kips)
Slide 26 Background: Previous Research on Support Conditions Sleeper/ballast contact patterns: (a) central void, (b) single hanging, (c) double hanging, (d) triple hanging, and (e) side-central voids Kaewunruen & Ramennikov, 2007
Slide 27 Crosstie Instrumentation Methodology Strains measured at the top and bottom of both rail seats and the crosstie center Bending moments can then be calculated at both rail seats and crosstie center
Slide 28 Crosstie Bending Moment Calculation Methodology Rail Seat 1 Tie Center Rail Seat 2 M ( railseat1) ( e e ) EI / d S2 S1 12 12 M ( center ) ( e e ) EI / d S4 S3 34 34 M ( railseat 2) ( e e ) EI / d S6 S5 56 56 Where, e: strain recorded from concrete surface gauge #1~#6 E: elastic modulus of concrete, 4500 ksi I: moment of inertia at each location d: the distance between the upper and lower gauges at each location
Slide 29 Instrumentation Location (Full Map) 1 2 3 4 A B C D E F G H I 5 6 7 8 9 10 11 12 P Q R S T U V W X Y Z 13 14 15 16 Rail Displacement Fixture Rail Longitudinal Displacement/Strains Pad Assembly Longitudinal Displacement Pad Assembly Lateral Displacement Insulator Longitudinal Displacement Insulator Vertical Displacement Steel Rods Vertical Web Strains Vertical and Lateral Circuits Shoulder Beam Insert (Lateral Force) Embedment Gages, Vertical Circuit, Clip Strains Crosstie Surface Strains MBTSS
Slide 30 Instrumented Crossties 1 2 3 4 A B C D E F G H I 5 6 7 8 9 10 11 12 P Q R S T U V W X Y Z 13 14 15 16
Slide 31 Concrete Crosstie Design Cracking Moment From CXT f c(28d)=11,730 psi Using f c=11,000 psi Positive: top in compression Negative: top in tension Mid-point - positive: 196.8 k-in - negative: -256.8 k-in Rail-seat - positive: 405.6 k-in - negative: -219.6 k-in
Moment (kips-in) Slide 32 Bending Moments Under Static Load: Rail Seats E and U and Crosstie Center E-U 0 kips 0-40 kips 50 40 30 20 10 0-10 -20-30 -40-50 0 10 20 30 40 Vertical Wheel Load (kips) Rail Seat E Rail Seat U Tie Center Design rail seat cracking moments positive: 405.6 k-in negative: -219.6 k-in Design tie center cracking moment positive: 196.8 k-in negative: -256.8 k-in Tie EU Rail Seat E Tie Center Rail Seat U
Moments (kips-in) Slide 33 Bending Moments Under Dynamic Load: Rail Seat C by Car Type 200 180 160 140 120 100 80 60 40 20 0 0 20 40 60 Speed (mph) due to flat spot on wheel Car Weight: 44 kips Car Weight: 260 kips Car Weight: 286 kips Car Weight: 315 kips Design rail seat cracking moments positive: 405.6 k-in Tie CS negative: -219.6 k-in Rail Seat C Tie Center Rail Seat S
Moments (kips-in) Slide 34 Bending Moments Under Dynamic Load: Crosstie Center C-S by Car Type 0-5 -10-15 -20-25 -30-35 -40-45 -50 0 20 40 60 Speed (mph) Car Weight: 44 kips Car Weight: 260 kips Car Weight: 286 kips Car Weight: 315 kips Design tie center cracking moment positive: 196.8 k-in Tie CS negative: -256.8 k-in Rail Seat C Tie Center Rail Seat S
Slide 35 Discussion on Support Length 40 kips 40 kips 40 kips 40 kips p= 0.9302 kips/in p= 0.9302 kips/in 0 10 20 30 40 50 60 70 80 90 100 Load and Support Conditions p= 1.739 kips/in p= 1.739 kips/in 0 10 20 30 40 50 60 70 80 90 100 Load and Support Conditions Moment (kips-in) 200 100 0-100 -200 140.2-0.0 140.2 Moment (kips-in) 200 100 0-100 -200 40.1 0.0 40.1 0 10 20 30 40 50 60 70 80 90 100 Moment Diagram 0 10 20 30 40 50 60 70 80 90 100 Moment Diagram Newly tamped track in UIC Reduced support length As crosstie support length is reduced, the resulting rail seat moment is reduced
Slide 36 Conclusions from Bending Behavior Analysis Experimentation Bending moments recorded during dynamic train runs are larger than those recorded during static tests In general, the recorded bending moment increased as the nominal car weight increased Impact loads can significantly effect the crosstie bending moments Bending moments recorded in field do not approach the cracking limit Low bending moments at rail seat may be due to a short support length in the field
Slide 37 Future Work Clip Performance Effect of cyclic loading on tangential and normal components of clamping force Effect of repeated impact load on tangential and normal component of clamping force Crosstie Performance Rail seat vertical load will be analyzed via concrete embedment strain gauges cast below the rail seat Rail seat vertical load and concrete crosstie bending behavior will be compared More detailed analysis of the effect of support conditions on concrete crossties bending
Slide 38 Acknowledgements Funding for this research has been provided by the Federal Railroad Administration (FRA) Industry Partnership and support has been provided by Union Pacific Railroad BNSF Railway National Railway Passenger Corporation (Amtrak) Amsted RPS / Amsted Rail, Inc. GIC Ingeniería y Construcción Hanson Professional Services, Inc. CXT Concrete Ties, Inc., LB Foster Company TTX Company FRA Tie and Fastener BAA Industry Partners:
Slide 39 Questions? Sihang Wei Graduate Research Assistant Department of Civil and Environmental Engineering University of Illinois, Urbana-Champaign Email: wei22@illinois.edu